1. Field of the invention
The present invention relates, generally, to lighting devices and, more specifically, lighting device in a motor vehicle.
2. Description of the Related Art
Various lighting devices for motor vehicles are known in the art. Motor vehicle lighting devices may be differentiated between head lights and other types of lights. Head lights are located in the front area of a motor vehicle and promote road safety, by making the vehicle visible to other traffic participants, and serve to illuminate the roadway in front of the motor vehicle. Head lights may be realized as a low beam light, a high beam light, a fog light, or any other kind of adaptive light distribution suitable to improve the vision of the motor vehicle driver (for example, a positioning light, motorway light, partial high beam light, marker light, etc.). The other types of lights known in the art primarily promote road safety by making the vehicle visible to other traffic participants. By way of example, front lights in the front area of the motor vehicle may include daytime running lights, indicator lights, or positioning lights, and rear lights in the rear portion of the motor vehicle include brake lights, rear lights, reverse lights, or indicator lights. The front lights can be integrated into a head light or formed and arranged as separate lights in the front area of the motor vehicle. Moreover, one light may perform several light functions, such as is commonly integrated into one rear light.
Lighting devices known in the art include at least of one light source for producing light, (for example, a light bulb, gas discharge lamp or semiconductor light source), and at least one primary optics for focusing the produced light. The primary optics can be made in form of a reflector (concave mirror) which reflects the light by common reflection, or as a translucent body made of glass of plastic material (a so-called “optical lens”) where the focusing of the light is achieved by optical refraction at the entry into the body and/or at the exit out of the body and/or by total internal reflection at the outer boundary surfaces of the body.
It is further common to use light conductors in lighting devices, where the entering light rays are propagated or transmitted by total internal reflection and are deflected via light coupling-out areas in such a way that they emit out of the light conductor at predefined light output areas. Thus, it is possible that the light—particularly in substantially rod-shaped light conductors—is coupled into the end faces of the light conductor. Further, it is also possible to couple light—additionally or alternatively—into an area along a longitudinal extension of the light conductor by a so-called “midway coupling-in”. A coupling of light into the light conductor, which is not performed via the end faces of the light conductor, is generally called a midway coupling-in.
Light conductors are frequently made in form of a translucent body of glass or plastic material. The material of the light conductor can be stiff or flexible to a certain degree. The light conductors can be used in a lighting device in a similar way like a light source, whereby there is a considerable scope with regard to the shape and form of the light conductor itself and of the light output area of the light conductor. Thus, there is a great variety of characteristic design options for the lighting device in the use of light conductors.
The term “midway coupling-in” is to be understood as the coupling-in of light into a rod-shaped light conductor at a random location, but not at the end faces. Preferably, light is coupled into visible areas of the light conductor. A midway coupling-in into a light conductor is known, for example, from DE 102010025208A1, which depicts a lighting device that includes a first light conductor with a light input area, a light coupling-out area, and a light output area. A second light conductor is designed to couple light into the first light conductor by a midway coupling-in. In order to accomplish this, the second light conductor with its light output area is substantially aligned tangential to the light input area of the first light conductor. Thus, both light conductors are connected in a form-fit manner. In one embodiment, both light conductors of the light conductor arrangement are formed as a one-piece injection molding component. However, this is relatively complex and demands extensive planning, in particular to enable a demolding of the one-piece light conductor arrangement. The production of the light conductor arrangement can be complicated by undercuts. Yet, it is also possible to produce the two light conductors separately.
The disadvantage of the lighting device with the common light conductor arrangement arises when the light conductor arrangement is made in several parts, which means that the light conductors are made separate from each other and the junction between the light conductors presents an interference point where light is coupled out of the light conductor in an undesired way. As a result, the efficiency or efficiency factor of the light conductor arrangement is reduced. Further, to an observer, the light emitted from the interference point in an uncontrolled way produces an inhomogeneous appearance of the light conductor arrangement. Further, in the cold condition, the junction is clearly visible as a dark area and creates an optically unpleasant, inhomogeneous appearance of the light conductor.
Thus, there remains a need in the art for a light conductor arrangement that includes at least two light conductors, where one of the light conductors couples light into the other light conductor by a midway coupling-in in a simple and cost-effective way, where the light conductors can be connected with each other in such a way that light from the one light conductor is efficiently coupled into the other light conductor.